1. Field of the Invention
The present invention relates to an image display apparatus, an image display method, and a program for projecting an image on a screen.
2. Description of the Related Art
Projectors project images on a screen. For example, the publication of Japanese Patent No. 3120526 (page 2-3, FIG. 4, FIG. 5) discloses a projector which combines an input video with a different image such as characters, figures, etc. and projects the combined video on a screen.
Further, another projector measures the distance to the screen to achieve the right focus in order to project a vivid video on the screen. As this kind of projector, Unexamined Japanese Patent Application KOKAI Publication No. 2003-153135 (page 3, FIG. 5) discloses one that comprises a passive auto focus unit (AF unit). This AF unit comprises a phase difference sensor that has two line sensors.
This projector projects a chart image for distance measurement purpose on the screen, and the phase difference sensor receives the light from this image so that the distance to the screen may be measured based on the phase difference of the chart image obtained by the phase difference sensor.
By combining this chart image on an input video, the projector can project a vivid video on the screen by controlling the focus at predetermined time intervals or when the distance to the screen changes due to shakes.
However, if such a chart image is overlaid on the video intended to be viewed, viewers get a strange feeling and the video may be unclear.
Therefore, it is desirable that this chart image be displayed in as small a size as possible.